Carbon dioxide,water vapor and sensible heat fluxes over a tallgrass prairie

Fluxes of CO₂, water vapor and sensible heat were measured in a grassland ecosystem near Manhattan, Kansas, employing the eddy correlation technique. The vegetation at this site is dominated by big bluestem (Andropogon gerardii), switchgrass (Panicum virgatum), and indiangrass (Sorghastrum nutans). Diurnal patterns of the energy budget components and CO₂ fluxes are evaluated on a few selected days. Influence of high atmospheric evaporative demand and low availability of soil water are examined on (a) energy partitioning, and (b) the magnitudes and patterns of atmospheric carbon dioxide exchange.Published as Paper No. 8470, Journal Series, Nebraska Agricultural Research Division.     

Actinic fluxes: The role of clouds in photodissociation

The role of clouds in photodissociation is examined by both modeling and observations. It is emphasized that the photodissociation rate is proportional to the actinic flux rather than to the irradiance. (The actinic flux concerns the energy that is incident on a molecule, irrespective of the direction of incidence. The irradiance concerns the energy that is incident on a plane.) A 3-layer model is used to calculate the actinic flux above and below a cloud, relative to the incident flux, in terms of cloud albedo, zenith angle and the albedo of the underlying and overlying atmosphere. Cloud albedo is mainly determined by cloud optical thickness. An expression for the in-cloud actinic flux is given as a function of in-cloud optical thickness. The 3-layer model seems to be an useful model for estimation of photodissociation rates in dispersion models. Further, a multi-layer delta-Eddington model is used to calculate irradiances, actinic fluxes and photodissociation rates of nitrogen dioxide J(NO₂) as a function of height in inhomogeneous atmospheres. For the considered wavelength interval [290–420 nm], Rayleigh scattering, ozone absorption and Mie scattering and absorption by cloud drops and aerosols should be taken into account. It is stressed that both models are one-dimensional and as such are unable to deal with partial cloudiness. It is shown that if no clouds are present, the actinic flux depends primarily on the solar zenith angle. The actinic flux usually increases with height. For cloudy atmospheres, another important parameter with respect to the actinic flux is added: cloud optical thickness, which determines cloud albedo. It can be shown that in-cloud characteristics and cloud height are less important in describing the effect of a cloud on the actinic flux (outside the cloud). The in-cloud values of the actinic flux can exceed the values outside the cloud. Finally, using the photostationary state relationship, good agreement is found between model results and aircraft measurements.     

Carbon dioxide fluxes over the atlantic ocean estimated from measurements at Tiana Beach,Long Island,New York

Mean carbon dioxide concentration-gradients were measured continuously for a period of three weeks during December 1978 at Tiana Beach, Long Island, with onshore atmospheric flows. The height interval was 20 m and the fetch over the sandy beach for onshore flows was about 20 m for low tides and near zero for high tides. Measurements at the beach were thus approximately representative of over-ocean atmospheric flows. Concentration differences for this height interval were found to vary from 0.75 to 2 ppm. Approximate computations indicated this local gradient to be about two orders of magnitude greater than the values estimated from global means.Authored under contract DE-ACO2-76CH00016 with the U.S. Department of Energy. The U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.     

Carbon dioxide and methane in the Arctic atmosphere

Fifty flask air samples were taken during April 1986 from a NOAA WP-3D Orion aircraft which flew missions across a broad region of the Arctic as part of the second Arctic Gas and Aerosol Sampling Program (AGASP II). The samples were subsequently analyzed for both carbon dioxide (CO₂) and methane (CH₄). The samples were taken in well-defined layers of Arctic haze, in the background troposphere where no haze was detected, and from near the surface to the lower stratosphere. Vertical profiles were specifically measured in the vicinity of Barrow, Alaska to enable comparisons with routine surface measurements made at the NOAA/GMCC observatory. Elevated levels of both methane and carbon dioxide were found in haze layers. For samples taken in the background troposphere we found negative vertical gradients (lower concentrations aloft) for both gases. For the entire data set (including samples collected in the haze layers) we found a strong positive correlation between the methane and carbon dioxide concentrations, with a linear regression slope of 17.5 ppb CH₄/ppm CO₂, a standard error of 0.6, and a correlation coefficient (r²) of 0.95. This correlation between the two gases seen in the aircraft samples was corroborated by in situ surface measurements of these gases made at the Barrow observatory during March and April 1986. We also find a similar relationship between methane and carbon dioxide measured concurrenty for a short period in the moderately polluted urban atmosphere of Boulder, Colorado. We suggest that the strong correlation between methane and carbon dioxide concentrations reflects a common source region for both, with subsequent long-range transport of the polluted air to the Arctic.     

Carbon dioxide emissions in a methane economy

Increasing reliance on natural gas (methane) to meet global energy demands holds implications for atmospheric CO₂ concentrations. Analysis of these implications is presented, based on a logistic substitution model viewing energy technologies like biological species invading an econiche and substituting in case of superiority for existing species. This model suggests gas will become the dominant energy source and remain so for 50 years, peaking near 70 percent of world supply. Two scenarios of energy demand are explored, one holding per capita consumption at current levels, the second raising the global average in the year 2100 to the current U.S. level. In the first (efficiency) scenario concentrations peak about 450 ppm, while in the second (long wave) they near 600 ppm. Although projected CO₂ concentrations in a methane economy are low in relation to other scenarios, the projections confirm that global climate warming is likely to be a major planetary concern throughout the twenty-first century. A second finding is that data on past growth of world per capita energy consumption group neatly into two pulses consistent with longwave theories in economics.     

Carbon dioxide capture and storage: a status report

Abstract

Fossil fuel combustion is the largest source of anthropogenic greenhouse gas (GHG) emissions. As a result of combustion, essentially all of the fuel carbon is emitted to the atmosphere as carbon dioxide (CO₂), along with small amounts of methane and, in some cases, nitrous oxide. It has been axiomatic that reducing anthropogenic GHG emissions requires reducing fossil-fuel use. However, that relationship may no longer be as highly coupled in the future. There is an emerging understanding that CO₂ capture and storage (CCS) technology offers a way of using fossil fuels while reducing CO₂ emissions by 85% or more. While CCS is not the ‘silver bullet’ that in and of itself will solve the climate change problem, it is a powerful addition to the portfolio of technologies that will be needed to address climate change. The goal of this Commentary is to describe CCS technology in simple terms: how it might be used, how it might fit into longer term mitigation strategies, and finally, the policy issues that its emergence creates. All of these topics are discussed in much greater detail in the recently published Intergovernmental Panel on Climate Change (IPCC) Special Report on Carbon Dioxide Capture and Storage (SRCCS) (IPCC, 2005).     

Carbon dioxide exchange in a temperate grassland ecosystem

Carbon dioxide exchange was measured, using the eddy correlation technique, over a tallgrass prairie in northeastern Kansas, U.S.A., during a six-month period in 1987. The diurnal patterns of daytime and nocturnal CO₂ fluxes are presented on eight selected days. These days were distributed throughout most of the growing season and covered a wide range of meteorological and soil water conditions. The midday CO₂ flux reached a maximum of 1.3 mg m^-2 (ground area) s^-1 during early July and was near zero during the dry period in late July. The dependence of the daytime carbon dioxide exchange on pertinent controlling variables, particularly photosynthetically active radiation, vapor pressure deficit and soil water content is discussed. The nocturnal CO₂ flux (soil plus plant respiration) averaged -0.4 mg m^-2 (ground area) s^-1 during early July and was about -0.2 mg m^-2 s^-1 during the dry period.Published as Paper No. 9061, Journal Series, Agricultural Research Division, University of Nebraska-Lincoln, U.S.A.Research Associate and Professor, respectively.     

Carbon dioxide emissions from Russia's electricity sector: future scenarios

Abstract

This article investigates future greenhouse gas emission scenarios for Russia's electricity sector, a topic of importance since Russia's ratification of the Kyoto Protocol in November 2004. Eleven scenarios are constructed to the year 2020 considering economic and technological details in both the demand and supply sides of the sector. The scenarios are based upon a thorough review of the different factors controlling carbon dioxide emissions, including potential economic growth, changes in energy efficiency and technological development, and that Russia may export large amounts of natural gas to European and Asian markets. The most likely scenario is that Russia will double industrial output over the next 10 years, increase energy efficiency in the demand sector, will remain consistent to the goals of the Energy Strategy 2020 and will implement more efficient technology in the electricity supply sector. Consequently, carbon dioxide emissions will still be 102 million tonnes below 1990 levels in 2010, representing a significant source for emission reduction credits available to be sold on international markets or transferred to the next crediting period.     

Limitations of an eddy-correlation technique for the determination of the carbon dioxide and sensible heat fluxes

A modified infrared CO₂ gas analyzer, a small thermocouple assembly, a heated-thermocouple anemometer for horizontal wind, and a propeller-type vertical wind sensor were used to measure the eddy fluxes of heat and CO₂ above a corn crop. Experimental results of these fluxes are discussed. The main sources of errors of the eddy fluxes using these instruments were estimated:

1. Sensors with a time constant of 0.5 s appear to be fast enough to detect most of the vertical CO₂ transfer as long as the sensors are located at least one meter above the crop surface.
2. The deviation from steady-state conditions for 10-min periods was found to have a significant effect on the eddy flux estimates.
3. Temperature fluctuations of the air sample passing through the CO₂ infrared gas analyzer were found to be non-negligible but could be easily corrected.
4. A 1° misalignment of the vertical anemometer affected these eddy fluxes by less than 10% under all circumstances studied.

     

Influence of hydrological regime on carbon dioxide fluxes over oligotrophic bog massif in northwestern Russia

It is found that the surface bog temperature and bog water level position are major factors that determine CO₂ emission from the bog massif. The emission intensity increases with increasing temperature and with a bog water level decrease. The dependence of CO₂ emission is shown to be different for each bog microlandscape. Monthly mean CO₂ emissions are given for the central bog massif in the years with different water content. Based on modeling, it is shown that in the case of a low bog water level the CO₂ flux is directed to the atmosphere (the emission value exceeds the gas amount consumed for photosynthesis), while in the case of a high level, it is taken up by the growing plants.     

Carbon dioxide and the δ18O record of late-Quaternary climatic change: a global model

A dynamical model for the late-Quaternary global variations of ¹⁸O, mean ocean surface tempeature , ice mass I, deep ocean temperature , and atmospheric carbon dioxide concentration , is constructed. This model consists of two diagnostic equations (for ¹⁸O and ), and three prognostic equations (for I, , and ) of a form studied extensively in previous articles. The carbon dioxide equation includes forcing by a representation of the Milankovitch earth-orbital radiation effects, and contains a basic instability that drives a free oscillation of period near 100,000 years. The system is constrained to conserve mass and energy, contain physically plausible feedbacks including a system time constant no greater than 10.000 years, and be robust (i. e., structurally stable in the presence of expected noise levels and uncertainties in values of coefficients). Within the limits of these constraints, coefficients are chosen such that (i) the solution gives a good fit to the observed SPECMAP ¹⁸O variations, and (ii) the ice mass variations are qualitatively similar to the ¹⁸O variations. The predicted long term variations of sea surface temperature and atmospheric carbon dioxide are in reasonably good agreement with the limited observational evidence available for these quantities, while the predicted variations of deep ocean temperature remain to be verified when paleoclimatic estimates of this quantity become available. The relative contributions of ice mass changes and surface water temperature changes to the variations of ¹⁸O at any time are given by the model.     

Seasonal variation of carbon dioxide fluxes over irrigated soybean (Glycine max L.)

In this study, variations in carbon dioxide (CO₂) fluxes resulting from gross primary production (GPP), net ecosystem exchange (NEE), and respiration (R _e) of soybean (Glycine max L.) were investigated by the Eddy Covariance method during the growing period from June to November 2005 on an irrigated sand field at the Arid Land Research Center, Tottori University in Tottori, Japan. Although climatic conditions were humid and temperate, the soybeans required frequent irrigation because of the low water holding capacity of the sandy soil at the field site. Finally, it has been found that the accumulated NEE, GPP, and R _e fluxes of soybean over 126 days amount to ?93, 319, and 226 gC m^?2, respectively. Furthermore, the average ratio of GPP to R _e was 1.4 and the average ratio of NEE to GPP was about ?0.29 for the growth period of soybean. Daily maximum NEE of ?3.8 gC m^?2 occurred when LAI was 1.1.     

Public support for carbon dioxide removal strategies: the role of tampering with nature perceptions

Climatic Change - Carbon dioxide removal (CDR) describes a suite of controversial approaches to mitigating climate change that involve removing existing carbon dioxide from the atmosphere. Through...     

Observations of the convective plume of a lake under cold-air advective conditions

Moderating effects of Lake Apopka, Florida on downwind surface temperatures were evaluated under cold-air advective conditions. Point temperature measurements north and south of the lake and data obtained from a thermal scanner flown at 1.6 km indicate that surface temperatures directly downwind may be higher than surrounding surface temperatures by as much as 5 °C under conditions of moderate winds (~4 m s^–1). No substantial temperature effects were observed with surface wind speed less than 1 m s^–1. Fluxes of sensible and latent heat from Lake Apopka were calculated from measurements of lake temperature, net radiation, relative humidity and air temperature above the lake. Bulk transfer coefficients and the Bowen ratio were calculated and found to be in agreement with reported data for non-advective conditions.IFAS Journal Series No. 1006.